The invention relates to a system for conveying objects.
The invention applies notably to the packaging of articles such as bottles or cans, generally cylindrical in shape.
It is known that the articles are first of all routed individually on a supply track up to a grouping station where the batches of articles are formed and then spaced apart in order to be transferred to a discharge track, along which they are wrapped or packed.
In order to form a space between two successive batches of articles, it is known that the batches of articles can be accelerated between the supply track and the discharge track.
In this regard, it is possible to cite notably the document GB-974 995.
The space then formed between the same faces of two consecutive batches is referred as the xe2x80x9cpitchxe2x80x9d or the xe2x80x9cmachine pitchxe2x80x9d.
Distributors are at the present time seeking to reduce their stocks whilst offering ever more diversified ranges of packaged products.
In addition, distributors require to be able to vary their offer within the same product range, by offering to consumers, for the same article, such as a bottle or a can filled with a beverage, varied packagings such as packs of two, three, four, six or eight articles or more.
In order to meet these requirements, manufacturers must be in a position to continually renew their machine ranges, so as to adapt them not only to the shapes of new products, and to their sizes and weights, but also to the size and shape of their packaging, usually cardboard blanks or equivalent.
At the present time manufacturers are offering distributors packaging solutions or machines which have many drawbacks.
Certain manufacturers are offering distributors one machine for each type of finished product, which is cumbersome and expensive.
Other manufacturers, for their part, are offering a machine for each range of products, which requires setting the machine according to the type of packaging required: batches of two, four, six, eight or more.
This is because, for a constant machine throughput (and therefore a constant input speed), it is necessary to adapt the output speed and/or the machine pitch.
The majority of machines do not have a pitch adjusting system. It is therefore necessary to increase the output speed, the pitch being fixed whatever the number of articles per batch, such as for example in the document DE 31 29 723.
Thus changing for example from a grouping by batches of twelve articles to a grouping by batches of four makes it necessary to triple the output speed of the machine, which is incompatible with the physical limits of the installations, and in particular the packaging devices.
Some machines have manual pitch adjusting systems, which requires as many manual actions as there are changes of product within the same range.
At the present time, the frequencies of these changes may attain two to three per day, a frequency which is difficult to attain by means of manual adjustments.
The invention aims at resolving notably the aforementioned drawbacks of the prior art, by proposing a conveying system which allows the automatic adjustment both of the machine pitch and of the production rate.
To this end, the object of the invention is a system for conveying objects, which comprises at least one endless transporter able to route the objects along a so-called transportation surface, the transporter comprising a plurality of pushers regularly spaced apart, fixed to a movable support for the pushers, continuously travelling, in a single direction and periodically along a closed-loop path which extends substantially in a so-called conveying plane, perpendicular to the said transportation surface, the path being locally contiguous with the transportation surface, each pusher being mounted so as to be able to move between a so-called inactive position in which the pusher is located at a distance from the transportation surface and does not project therefrom, and a so-called active position in which it projects at least partially from the transportation surface in order to come into engagement with an object and push this object along the said surface, so that it is possible to vary the number of pushers simultaneously in the active position.
According to one embodiment, the said conveying system comprises:
a means of driving the support means;
a movable member for actuating the pushers in order to cause them to pass from their inactive position to their active position at the transportation surface;
a means of driving the said actuating member;
a device for controlling the drive means.
The control device is arranged to apply notably to the means of driving the support means and/or to the means of driving the actuating member, a speed profile chosen from amongst a preprogrammed set of speed profiles.
For example, the control device is arranged to apply to the means of driving the actuating member a speed profile such that the operation of the actuating member is periodic, the period of the actuating member being defined as the interval of time separating two successive passages of the actuating member through the same position.
The period of the transporter being defined as the interval of time separating the passage of two pushers through the same point on the path, the control device is for example arranged so that the period of the actuating member is a multiple of the period of the transporter.
According to one embodiment, the said movable support is an endless chain meshing with two pinions, at least one of which is slaved to the control device.
Whilst each pusher is, for example, in the form of a rigid piece which comprises a first branch able to come into engagement with the drive member, and a second branch substantially perpendicular to the first, able to project at least partly from the transportation surface in order to be able to come into engagement with an object.
According to one embodiment, the second branch has a surface substantially perpendicular to the said conveying plane and which, when the pusher is in its active position, extends substantially perpendicularly to the transportation surface in order to come into contact with the object.
In addition, each pusher comprises for example a shaft substantially perpendicular to the conveying plane, forming a means of fixing the pusher to the support means, and about which the pusher is able to pivot, in order to pass from its inactive position to its active position, or vice-versa.
According to one embodiment, the transporter comprises a guide rail which extends substantially in the conveying plane, substantially along the path defined by the support.
The guide rail can comprise, substantially along the transportation surface, a first so-called top track for guiding the pushers, contiguous with the transportation surface, and a second so-called bottom track for guiding the pushers, parallel to the first.
Each pusher for its part can comprise, alone or in combination:
at least one first toe, projecting from the first branch substantially perpendicularly to the conveying plane, able to cooperate with the bottom track when the pusher is in the inactive position, and with the top track when the pusher is in the active position;
at least one second toe, projecting from the first branch perpendicularly to the conveying plane, able to cooperate with the top track when the pusher is in the inactive position.
According to one embodiment, the transporter has a so-called switching zone where the guide rail is interrupted, and in which the pushers are able to pivot about their shaft in order to pass from their inactive position to their active position.
The actuating member, for its part, can comprise a cam extending substantially in the conveying plane close to the said switching zone, and driven in rotation in this plane about a shaft substantially perpendicular to this by the said drive means, passing through a first angular position in which the said cam engages at least one of the pushers in order to cause it to pivot about its shaft from its inactive position to its active position when passing through the switching zone, and a second angular position in which the said cam releases the pusher.
For example, the cam is arranged to come momentarily into engagement with the second branch of the pusher in order to cause the latter to pivot whilst switching its first toe from the bottom track to the top track.
According to a first arrangement, the control device is arranged to apply, to the said drive means, a continuous periodic speed profile which is variable according to the angular position of the cam, this speed being:
of constant sign, so that the cam rotates in a single direction in the same direction as the movable support means;
substantially constant and equal to a first value between the first and second angular positions of the cam;
the cam rotates at a non-constant speed, increasing and then decreasing between the second and first angular positions of the cam.
According to a second arrangement, the control device is arranged to apply to the said drive means a continuous periodic speed profile which is variable according to the angular position of the cam, this speed being:
of constant sign, so that the cam rotates in a single direction in the same direction as the movable support means;
substantially constant and equal to a first value between the first and second angular positions of the cam;
the cam rotates at a non-constant speed, increasing and then decreasing between the second and the first angular positions of the cam.
For example, this speed profile is chosen from amongst a preprogrammed set of speed profiles such that the actuation means selectively engage a certain number of successive pushers belonging to a predetermined subset of the set of pushers.
According to one embodiment, the means of driving the support means and/or the means of driving the actuating member comprise at least one motor whose rotation speed is continuously adjustable, such as an electric motor, of the brushless DC type.
Other objects and advantages of the invention will emerge during the following description of embodiments, a description given with reference to the accompanying drawings, in which: